Telephone system



March 5, 1946. s. M. BABCOCK ET AL 2,396,072

TELEPHONE SYSTEM Filed April 25,. 1942 $.14. BA BCOCK I/VVE N TORS A. W HOR TON JR.

By M A.LOGAN ATTORNEY elude two party lines to provide a Patented Mar. 5, 1946 7 2,396,012 TELEPHONE SYSTEM- uularso STATES OFFICE; I

StuartMf. Bab'cock; Chatharn; South Orange, and Summit, N. J'.,- assignor's rthur Hbr'ton, Mason A: Logan: t'd Belt Telephone Laboratories, Incorporated; New York, N. Y.,la corporation of- New York y This invention relates itotelepl'ione systems and anyJ arrangement for identifyingthe calling "station which does not requirea' ground' connection is, in this respect, a more desirable arrangement. It is. furthervkn'own that voice currents; that is currents generated in telephone transmitter circuits and transmitted'thr'ough a connected telephone line; are I the amplitude of the negative half cycles of current bein'gi greater than that of the; positive half cycles of 5 current or vice versa, depending upon the particular circuit arrangement' at a subscrib'ers station.

Thi'sin'vention is'a means for identifyingthe calling station on a two-party line whichutilizes the asymmetric character of the voice currents transmitted over the line from'the calling station to identify the calling station, the substation circuit'arrangements at the two stations being such that the negative half cycles .ofthe voice currents transmitted'over the line from one 'of' thestations' are of larger amplitude than'the positive half cycles and that the positive half cycles of the voice currents transmitted over the line from the other station are of larger amplitude than. the negative half'cycles.

According to a feature of "the invention the twor stations. of a two-party line are arranged sothat the voice currents transmitted over the line fromonelofthe stations differs in character from the voice currents transmitted from the otherof the stations in that'th'e amplitude of the positive'half cycles areof the greater amplitude in the. one case and. the negative half cycles are .of the greater amplitude in the other case.

According to a'further feature'of the invention means is provided in the central'oflice for determining 7, whether the positive half cycles of voice currents ,cransmi ted 'oi'rer'i a calling party.

not symmetrical in wave form,

line are larger or'sm'aller'tlri'an'the.negativehalf cycles, thereby identifying" the particular oneor twostations on thefli'newlri'icl'i' is engaged inco'riversation over the line. I

A- clear and complete understanding of the invention will be 'facilitatetlfby 'cbn's'ide'ring'a telephone system embodying the features' of 'theinventiori, one such systeinheing "represented schematioa'llyin'the drawing which formsa parrot this specification;

The drawing; which consists of a singlef figure, shows a system comprising two; telephone supscri'bersstations A" Ll L a' subscribers station" X T connected" wa'" line Lx' and a central office" 001 comprising a epeatingf'coil' "and"a'n asym'nrietry'detectorA1); q The stationsA" and B are "of the -centralfbat tery type." Station A comprises a tran's'in'Fitter l I, receiver l2, switch" 13 actuate'd by removal of the transmitter and receiver from their "normal support, induction coil' I4; condenser l5; ringer l'6andf ringing' condenser Hi 7 StationB c'o'nip'rises" like elements and, in addition; a network consisting of induction coil '28a'nd condenser; 29.

' By .p'rovidin'gsuch 'a'network atst'ation B and-not providing" such a network at, station? A; the" amplitude of the positive-half cyclesforftheurrent r the negative half cycles A generated by one-or transmitters H and 2]; and

in; line L! will v belarger than the amplitud -i 0f 7 theam-plitud'e of'the" negative "half cycles "of the current in linefL'twil'l be larger than the aniplitude of the positive half "cy'cles when this current is'generated by. the"other' of transmitters-'11 andZls. v H

The repeating coil-Kill and; detectorfADmay be indivi'dualnto the-line 'L I -but arepre'ferably *conimon' to --a"p1ura1ity of lines, a {may constitute a' part of a trunk or selecto'r circuitthrough' which a "desired connectionis established between the calling lineLFand any called-line and subscribers'station'X'in the system. irramanual telephone systemthe detectorAD may be"a*part of an operator's positionequipment; and aidial transformer 40 the primary "telephone system "the detectof'AD "maybe-individual to a trunk or selector circuit or common to'a group of such circuits. Thedetect6r"AD mayibe associatedwith 'a calling line L1 only while the calling station is being identified;

Thaasymmetry detector AD comprises'anjiriput I g I windin'gfof which'is connected to; a"cal1ing line L"! variaple mu amplifier tubes 4| and'lz; transformerdfiflinear amplifier'tub'esf il and 52, transformer: ainpliiiefdjetectortubes 5| "amtrandremys 1| and 12".- The and B" connectedto a line when" this' currentis speech voltages transmitted over line LI and applied through transformer 4|] to the grids of amplifier tubes 4| and 42, ar further amplified by tubes 5| and 52 and then applied through transformer to the grids of self-biasing detector tubes 6| and 62. The voltages applied through transformer 55 cause rectified currents in the grid-cathode circuits of tubes El and 62, thereby efiecting the charging of condensers 63 and 64; so that the bias of both of these tubes is increased until the efiective grid voltage is almost equal to the peak voltage of the applied signal. With voice current of asymmetric wave form in line Ll, th final, small current which maintains the charge in condensers 63 and 64, results from the highest positive peak voltage; and the grid of that one of tubes 6| and 62, to which this peak voltage is applied, is less negative than the grid of the other of these tubes. Therefore, the current in the anode-cathode circuit of the detector tube to which th highest positive voltage is applied will be larger than the current in the anode-cathode circuit of the other of these detector tubes. A portion of the self-biasing voltage developed by detector tubes 6| and 62 is included in the bias of the variable mu amplifier tubes 4| and 42 to supply an automatic sensitivity control so that the linear amplifier tubes will not be overloaded by loud speech or tones. The current in th output circuit of tube 6| energizes the middle winding of relay H and upper winding of relay 12 in series; and. the current in the output circuit of tube 62 energizes the middle winding of relay l2 and lower winding of relay 1| in series. Relays H and 12 are polarized relays, each of which has a biasing winding for normally holding the contact springs in the position shown. If the negative and positive half cycles of current in line Ll were of like amplitude, the middle and lower windings of relay .H would be substantially equally and difieren- 'tially energized and the middle and upper windings of relay 12 would be substantially equally and difierentially energized, so that neither relay 7| nor relay 12 would be operated. Condenser 13 bypasses the alternating current components of the detected signal and permits only the direct current components to pass through the differential windings of relays 7| and 72. If, however, the current transmitted through line LI- and transformer 40 to detector AD results from speech at the one or theother of stations A and B, the asymmetric character of this current will effect the operation of relay 1| in the one case and relay 12 in the other case. If relay 7| operates, it closes a circuit for operating relay 8| to indicate that station A is the calling station; and if relay 72 operates, it closes a circuit for operating relay 82 to indicate that station B is the calling station. Relays 8| and 82 may control the operation of the message registers which are individual to the stations A or B, if these stations are message rate stations; or control whatever other operations are desired.

Since, in a dial system, the calling subscriber does not talk until the called subscriber answers and speech currents from the called station would interfere with the calling party test, it is necessary to further provide means for applying to the asymmetry detector speech currents from the calling station but not from the called station. To this end directionally selective coils similar to those disclosed in the patent to Meszar. No. 1,835,802, granted December 8, 1931, may be inserted between the calling line and the repeating coil 39 to prevent speech currents from the called line from affecting the party line test which is made by the asymmetry detector.

What is claimed is:

1. In a telephone system, subscribers lines, a calling line, two stations connected to said line, means including a link circuit for completing talking connections between calling and called lines, means connecting said calling line to said link, means at one of said stations polarizing in one direction the speech currents transmitted therefrom, means at the other of said stations polarizing in the other direction the speech currents transmitted therefrom, and means comprising an asymmetry detector associated with said link for determining the polarity of asymmetry existing in the speech currents transmitted from the calling station, thereby to identify the calling station.

2. In a telephone system, subscribers lines and stations, each of said stations including a transmitter, one of said lines being a party line serving two of said stations, the transmitter circuit at said two stations being arranged so that the speech currents transmitted over the line are asymmetrical in wave form, the amplitude of the positive half cycles of the speech currents transmitted from one of said stations being larger than the amplitude of the negative half cycles and the amplitude of the negative half cycles of the speech currents transmitted from the other of said stations being larger than the amplitude of the positive half cycles, means including a link for completing talking connections between calling and called lines, means associated with said party line when a call is made, from either of said two stations for identifying the calling station by determining whether the speech currents therefrom are polarized in the one direction or in the other direction.

3. In a telephone system,subscribers lines, a party line, two stations connected to said line, mean including a link circuit for establishing talking connections between calling and called lines, means responsive to the initiation of a call at either one of said stations for connecting said line to said link, the speech currents transmitted over said line from each of said stations being asymmetric in wave form, means at one of said stations for polarizing the speech currents transmitted therefrom in the opposite direction to that in which the speech currents transmitted from the other of said stations are polarized, and means associated with said link circuit for determining the direction in which the speech currents transmitted from the calling station are polarized, thereby to identify the calling station.

4. In a telephone system, subscribers lines in. cluding a party line, two stations connected to said line, means including a link circuit for completing connections between calling and called lines, means responsive to the initiation of a call at either one of said stations for-connecting said party line to said link, a transmitter circuit arrangement at one of said stationseffective to polarize the speech currents transmitted therefrom in one direction, and a transmitter circuit arrangement at the other of said stations effective to polarize the speech currents transmitted therefrom in the other direction.

5. In a telephone system, subscribers lines, a calling line, two stations connected to said line, mean including a link for completing connections between calling and called lines, means connecting said calling line to said link, means at rents transmitted therefrom in one direction,

means at the other of said stations polarizing the speech currents transmitted therefrom in the other direction, means comprising an asymmetry detector associated with saidlink for determining the polarity of asymmetry eiiisting in the speech currents transmitted from the calling'station, and means controlled by said asymmetry detector for indicating which of said stations is the calling sta- 151011. 1";

6. In a telephone systenj, subscribers lines. includinffg a party line, two stations. connected to said line, means includinga link circuit for completing connections between calling and called lines, means responsive to the initiation of a call 10 from said other station.

STUART M. BABCOCK. ARTHUR W. HORTON, JR. MASON 1A. LOGAN. 

